Definite's Extractor

My findings on Life, Linux, Open Source, and so on.

Monthly Archives: November 2015

SELinux for synergy , or generally other tcp/udp services

If you enforcing your SELinux and set your user to non unconfined_u, like either user_u or staff_u. You may found that your synergy or other tcp/udp service stop working. That is because your role cannot listen the ports that your services required.

To allow users to run TCP servers (bind to ports and accept connection from the same domain and outside users), run:

sudo setsebool selinuxuser_tcp_server 1

and for UDP:

sudo setsebool selinuxuser_udp_server 1


  1. user SELinux Policy documentation (8)

Fedora: maven-gpg-plugin keep asking passphrase

When doing maven release, maven-gpg-plugin keep showing

請輸入密語: [INFO] gpg: gpg-agent 在此階段無法使用
Enter passphrase: [INFO] gpg: gpg-agent is not available in this session

I literately has to input passphrase dozens (if not hundreds) times. Indeed annoying.

This is because Bug: gpg-1 cannot locate gpg-agent >= 2.1 . But I don’t really want to wait for the package fix. Luckily, gpg2 works, and there is a way to change what maven-gpg-plugin invokes. In other words. add following sections to your ~/.m2/settings.xml

<!-- No need to enter passphrase here, gpg-agent should be working now

Note that RHEL 7 does not suffer this problem, as in RHEL 7, gpg is actually gpg2. You can use

gpg --version

to verify it.

cmake-fedora-2.4.3 is released

cmake-fedora consists CMake modules and scripts that simplify and automate the release process for software package, especially for Fedora and EPEL.

Even if you are not using CMake on your packages, you can still using following scripts to simplify your package chores. For examples, if you want your packages to be build in koji and submit to bodhi in all active branches like rawhide, f23, f22, f21, simply run

cmake-fedora-fedpkg <SRPM>

It builds the SRPM on all the active branches, skip the already built ones, then submit them to bodhi.

Why some teachers say 5×3 does not mean 5+5+5

A child was marked as incorrect for translating “5×3” to “5+5+5” on a grade school math test.

Further discussion is at

According to Common Core: Represent and solve problems involving multiplication and division,  5×3 should be interpret as 5 groups of 3 objects each, which means 3+3+3+3+3.

I think this come from how every-day English express this kind of thing. Like 5 apples (apples appear 5 time), and 5 3’s is similar (3 appears 5 time). This also affect the definition of multiplicand and multiplier. Quote from Wikipedia Multiplication

When thinking of multiplication as repeated addition, the number to be multiplied is called the “multiplicand”, while the number of addends is called the “multiplier”.

In other world, 5×3 should be read as:

3 multiplied by 5

But for division, 5 ÷ 3 is read as:

5 divided by 3

IMHO, this is indeed confusing and inconvenient. If a teacher trying to teach multiplication using the word “multiplied” with blackboard and chalk, she need to

  1. Write 3 first, and say “three”
    Become:  3
  2. Write ×,  and say “multiplied by”
    Become: × 3
  3. Write 5, and say “five”
    Become: 5 × 3

Right to left writing, which is not a usual practice in English.

If the teacher  insists on left to right writing, she has to say “three” when she write “five”. 😛

Luckily, we have times to rescue. 5×3 should be read as:

5 times 3